Using these key or index fossils as markers, Smith could identify a particular layer of rock wherever it was exposed.

Because fossils actually record the slow but progressive development of life, scientists use them to identify rocks of the same age throughout the world.

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Because of the distortions and lies spread by fundamentalists about scientific dating there is a need for a centralized source of information on the topic.

A few examples of such lies are presented at the very bottom of this page.

The most compelling argument for an age of the earth of 4.5 billion years are the large number of independent tests that have been used to confirm this date.

These tests have been performed on what are thought to be the earth's oldest surviving rocks, meteorites, and moon rocks.

See more information about "Strata" Smith and his original geologic map of England.

Information about Simon Winchester's delightful biography of Smith, The Map That Changed the World is available at Tree-Ring dating is based on the principle that the growth rings on certain species of trees reflect variations in seasonal and annual rainfall.A short but clear explanation about radioactive isotopes commonly used for determining ages of rocks (with graphics) and putting numbers on the geologic time scale, extending it back before the occurance of abundant index fossils.This is a relatively new method intended to to improve the precision of uranium and thorium istopy methods.However, human beings love to see factual precision, and we want to know how old something is.Please remember that all dating methods, even those termed "absolute," are subject to margins of error. That is a very small amount of possible error range. Modern studies almost always use two or more methods to confirm dating work and to build confidence in the results obtained.Cross-dating is a technique used to take advantage of consistencies in stratigraphy between parts of a site or different sites, and objects or strata with a known relative chronology.